Effects of relative humidity and particle and surface properties on particle resuspension rates

Wind tunnel experiments examined the coupled effects of relative humidity (RH) and surface and particle properties on aerodynamically induced resuspension. Hydrophilic glass spheres and hydrophobic polyethylene spheres similar to 20 mu m in diameter, with nanoscale surface features, were resuspended from hydrophilic glass, hydrophobic chemical agent resistant coating (CARC), and gold surfaces. Roughness of the glass and gold surfaces was on the nanoscale, whereas CARC surfaces had microscale roughness. Different particle-surface combinations yielded van der Waals interactions that varied by a factor of 4, but these differences had a relatively minor effect on resuspension. Wind tunnel RH was varied between 7% and 78%. Overall, RH affected the resuspension of hydrophilic particles on hydrophilic surfaces most strongly and that of hydrophobic particles on hydrophobic surfaces the least. For each particle-surface combination there was a threshold RH value below which resuspension rates were essentially constant and in good agreement with a dimensionless model of particle resuspension. Copyright (c) 2016 American Association for Aerosol Research